Oligonuclear tricarbonylchromium- and tricarbonyltungsten derivatives of tris(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)(3), and related ligands

A series of trinuclear carbonylmetal complexes of tri(1-cyclohepta-2,4,6-tr ienyl)phosphane P(C7H7)(3) (1), has been prepared by the reaction of P(SiMe 3)(3) with eta(7) tropylium halfsandwich salts, [(eta(7)-C7H7)M(Co)(3)]BF4, (M = Cr, Mo, W). While phosphorus remains uncoordinated in the chromium co mplex P[(eta(6)-C7H7)Cr(CO)(3)](3) (2a), the molybdenum and tungsten analog ues, P[(eta(4)-C7H7)M(CO)(3)][(eta(6)-C7H7)M(CO)(3)](2) (M = MO (2b), W (2c )), contain a coordinated phosphorus atom together with a eta(4)-norcaradie nyl substituent. Reaction of 2a with pentacarbonylmetal fragments, [M(CO)(5 )], leads to trinuclear products, P[(eta(2)-C7H7)M(CO)(4)][( eta(6)-C7H7)M( CO)(3)](2) (M = Cr (5a), W (5c)), in which phosphorus is coordinated next t o an eta(2)-cycloheptatrienyl substituent. Several alkyl- and arylphosphane s containing [(eta(6)- C7H7)Cr(CO)(3)] substituents (X), e. g. Ph2P(X) (6a) , RP(X)(2) (R = Me (7a), CH2Ph (8a), Ph (9a)) and (X)(2)P(R')P(X)(2) (R' = methylene (10a) or o-phenylene (11a)), have also been synthesized. The chro mium complexes 6a - 11a contain an uncoordinated phosphorus center, but in contrast to 9a, the corresponding tungsten compound PhP[(eta(4)-C7H7)W(CO)( 3)][(eta(6)-C7H7)W(CO)(3)](2) (9c) has again a structure similar to 2c. The arsenic complexes, As[(eta(6)-C7H7)M(CO)(3)](3) (M = Cr (12a), W (12c)) bo th contain an uncoordinated arsenic center, analogous to 2a. The molecular structures of all new complexes in solution at room temperature were deduce d from a consistent set of H-1, C-13 and P-31 NMR data, and X-ray structure determinations were carried out for 2a and 5c.